1. Field of the Invention
The invention relates to a stylo pen tip with a front part supporting a writing tube, wherein the front section of a writing fluid cartridge is mounted from behind. The writing fluid cartridge has a closure element which is to be released by the front part when the front part is inserted into an operating position, within the writing fluid cartridge. An area of the cartridge front end has a reduced, elastically stretchable opening cross section which, in the operating position, grips behind a protrusion area that is formed on the front part. The outer diameter of the front part, in the area ahead of the protrusion area, is less in the operating position of the front part than the maximum diameter of the opening cross section.
2. Brief Description of the Prior Art:
In a known stylo pen tip, (German Letters Patent 37 09 918) a stretchable opening cross section of the writing fluid cartridge is, when in the operating position, in a practically unreleasable contact, with the front part. In other words, the stretchable opening cross section grips the protrusion area of the front part from behind, so that the user no longer can separate the two elements. It is intended thereby, to prevent the user from producing an unsuitable combination of writing fluid cartridge and front part. For example, the front part may be designed in such a way that it normally will not function, or remain sufficiently clear, after the writing fluid in a writing fluid cartridge has been used up.
A stylo pen tip is known (French Letters Patent 1 048 243), where an enlargement, in the form of either an approximately lens-shaped head or an annular rib, has been provided at the rear of the front part. This enlargement comes into engagement with a correspondingly formed annular end area of the writing fluid cartridge when the end of the front part is pushed into the front of the writing fluid cartridge. In this manner, a ball-shaped closure is displaced into the interior chamber of the writing fluid cartridge and is held secure, against being pulled out. The insertion movement is limited by the contact of a front part projection with the writing fluid cartridge that radially extends beyond the front edge of the writing fluid cartridge. Due to this shape of the protruding area on the front part and the elasticity to the material of the writing fluid cartridge, the user can separate the two parts by hand. However, there is a danger that such a separation will take place unintentionally. Even if a separation is performed on purpose, it is possible that during separation there will be a sudden displacement of the two parts, causing remaining writing fluid to be spilled.